CN106469988B - Power circuit of sewing machine motor - Google Patents

Abstract

The invention performs appropriate control according to the voltage or the number of phases of the AC power supply. The disclosed device is provided with: a 1 st diode bridge connected to an alternating current power supply; two capacitors connected in series between two outputs of the 1 st diode bridge; a switching unit for switching the middle of the two capacitors and one input unit of the 1 st diode bridge to a short-circuit state and an open-circuit state; a 2 nd diode bridge having two input parts connected to the ac power supply in parallel with the 1 st diode bridge; a voltage detection unit for detecting voltages of two output units of the 2 nd diode bridge, the present invention includes: a determination unit that obtains a duration of a minimum potential when the voltage detected by the voltage detection unit continuously changes, and determines whether the switching unit is in the voltage doubler rectification state or the full-wave rectification state based on the duration of the minimum potential; and a motor control unit for controlling the output of the sewing machine motor according to the rectification state obtained by the determination unit.

Description

Power circuit of sewing machine motor

technical field

The invention relates to a power supply circuit of a sewing machine motor.

Background technique

For the AC power used in each country or region, the standard is not uniform about the voltage, the total number of single-phase and three-phase, and it varies in each country and each region. For example, the voltage is roughly divided into a voltage range of 100 to 120V (hereinafter, referred to as a 100V voltage range) and a voltage range of 200 to 240V (hereinafter, referred to as a 200V voltage range).

A conventional power supply circuit for rectifying an AC power supply voltage includes a diode bridge having two input parts connected to the AC power supply and two output parts connected to a load; and two capacitors connected in series to the diode bridge between two output parts of the ; and a switch that switches between two capacitors and one input part of the diode bridge between a short-circuit state and an open-circuit state (for example, refer to Patent Document 1).

In this power supply circuit, full-wave rectification can be performed when the switch is in the open state, and voltage doubler rectification can be performed when the switch is in the short-circuit state.

Then, for the AC power supply in the 100V voltage range, the switch is operated in a short-circuit state to perform voltage doubler rectification, and for the AC power supply in the 200V voltage range, the switch is operated in an open state to perform full-wave rectification.

Patent Document 1: Japanese Patent Application Laid-Open No. 11-285253

However, the above-described conventional power supply circuit does not have a mechanism for externally identifying the voltage or phase number of the AC power supply, which rectification of full-wave rectification and voltage doubler rectification is being performed, and the like. Therefore, when applied as a control circuit of a sewing machine motor, appropriate control cannot be performed in accordance with the voltage of the AC power supply, the number of phases, and the like.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a power supply circuit for a sewing machine motor that can be appropriately controlled in accordance with the voltage or the number of phases of an AC power supply, the present invention having the following (1) or (2) any feature.

(1)

A power supply circuit for a sewing machine motor, characterized in that it has:

a first diode bridge having two input parts connected to an AC power supply and two output parts connected to a load;

two capacitors connected in series between the two outputs of the first diode bridge;

a switching part, which switches the middle of the two capacitors and one input part of the first diode bridge to a short-circuit state and an open-circuit state;

a second diode bridge having two input parts connected to the AC power supply in parallel with the first diode bridge; and

a voltage detection unit that detects the voltages of the two output units of the second diode bridge,

The power circuit of this sewing machine motor has:

A determination unit that obtains the duration of the minimum potential when the detection voltage of the voltage detection unit continuously changes, and determines whether the switching unit is in a voltage-doubling rectification state or a full-wave rectification state according to the duration of the minimum potential make a determination; and

The motor control unit performs output control of the sewing machine motor based on the rectification state obtained by the determination unit.

(2)

In the power supply circuit of the sewing machine motor according to the above (1), it is characterized in that:

The determination unit obtains the duration of the maximum potential when the detection voltage of the voltage detection unit continuously changes, and determines the number of phases of the AC power supply based on the duration of the maximum potential,

The motor control unit performs output control of the sewing machine motor based on the number of phases of the AC power source obtained by the determination unit.

effect of invention

The power supply circuit of the present invention can recognize which voltage range of the AC voltage of the AC power supply is, and the motor control unit can control the sewing machine motor so as to further reduce the load of the AC power supply according to the voltage range of the AC voltage.

In addition, even when the sewing machine motor is supplied with power by being connected to an AC power supply of a facility such as a sewing factory that uses a plurality of sewing machines, the occurrence of voltage drop (voltage fluctuation) in the power supply can be reduced, and a plurality of sewing machines can be A sewing machine makes good sewing.

Description of drawings

FIG. 1 is a block diagram showing a power supply circuit of a sewing machine motor as an embodiment of the invention.

FIG. 2 is a graph showing the waveform of the detection voltage when the AC power supply is in the single-phase 100V voltage range.

FIG. 3 is a graph showing the waveform of the detected voltage when the AC power supply is in the single-phase 200V voltage range.

FIG. 4 is a graph showing the waveform of the detected voltage when the AC power supply is in the three-phase 200V voltage range.

Description of the label

10 Power circuit

11 Sewing machine motor

12 AC Power

20 1st diode bridge

21, 22 Input section

23, 24 Output part

25～28 Diode

30 2nd diode bridge

31, 32 Input section

33, 34 Output part

35～38 Diode

41, 42 Capacitors

43 Manual switch (switching part)

44 Voltage detection section

45, 46 Resistors

51 Three-phase rectifier circuit

52 Motor drive circuit (motor control part)

53 Judgment Section

Th maximum potential time (duration of maximum potential)

Tl Minimum Potential Time (Duration of Minimum Potential)

Vh maximum potential

Vl minimum potential

Detailed ways

[Outline of Embodiment of Invention]

Hereinafter, as an embodiment of the present invention, the power supply circuit 10 of the sewing machine motor will be described based on the drawings. The power supply circuit of the sewing machine motor performs power supply and output control to the sewing machine motor 11 which is a sewing drive source of the sewing machine.

The voltage and number of phases of the AC power supplied to the sewing machine vary by country and region.

Here, the following three types of AC power sources are used as an example for description: (1) single-phase 100V voltage range (100-120V), 50Hz; (2) single-phase 200V voltage range (200V) ~240V), 50Hz; and (3) three-phase 200V voltage domain (200 ~ 240V), 50Hz.

The power supply circuit 10 of the sewing machine motor is converted into a DC voltage of 280 V suitable for driving the sewing machine motor 11 when connected to any of the above-mentioned three AC power supplies, and supplies power. However, in any of the above-mentioned (1) to (3), if the sewing machine motor 11 is driven with the same output, in the order of (1), (2), and (3), The burden increases.

Therefore, for example, in an environment where sewing machines are industrially used and a large number of sewing machines are operated simultaneously in a factory, in the case of the AC power sources of (1) and (2), the load becomes excessive, and the voltage of the power supply may drop. (voltage fluctuation).

Therefore, the purpose of the power supply circuit 10 for the sewing machine motor described above is to determine the voltage and the number of phases of the AC power supply, and to appropriately control the output of the sewing machine motor 11 .

[Schematic structure of power supply circuit of sewing machine motor]

FIG. 1 is a block diagram of a power supply circuit 10 of a sewing machine motor.

As shown in the figure, the power supply circuit 10 of the sewing machine motor includes a first diode bridge 20 including two input parts 21 and 22 connected to the AC power supply 12 and two output parts 23 connected to a load (sewing machine motor side) , 24; two capacitors 41, 42, which are connected in series between the two output parts 23, 24 of the first diode bridge 20; a manual switch 43 as a switching part, which connects the two capacitors 41, 42 and the One input part 22 of the first diode bridge 20 is switched between a short-circuit state and an open state; the second diode bridge 30 includes two input parts 31 connected to the AC power supply 12 in parallel with the first diode bridge 20 , 32; a voltage detection unit 44 which detects the voltages of the two output units 33 and 34 of the second diode bridge 30; and two resistors 45 and 46 which are connected in series to two of the second diode bridge 30 between the output units 33 and 34 .

[1st diode bridge]

The first diode bridge 20 includes a diode 25 that connects the anode terminal to the input unit 21 and the cathode terminal to the output unit 23 , and a diode 26 that connects the anode terminal to the output unit 24 and the cathode terminal to the input unit 21 Connections; a diode 27 which connects the anode terminal to the input part 22 and the cathode terminal to the output part 23; and a diode 28 which connects the anode terminal to the output part 24 and the cathode terminal to the input part 22.

The output unit 23 and the output unit 24 of the first diode bridge 20 are connected to the input unit of the three-phase rectifier circuit 51 . In addition, two capacitors 41 and 42 connected in series are bridged between the output unit 23 and the output unit 24 .

The sewing machine motor 11 is an AC servo motor, and the three-phase rectifier circuit 51 further optimizes the current rectified by the first diode bridge 20 and the capacitors 41 and 42 for driving the AC servo motor.

The three-phase rectifier circuit 51 includes two diodes 511 and 512 connected in series, and the anode terminals of these diodes are directed to the output unit 24 side, and the cathode terminals are directed to the output unit 23 side.

In addition, when the AC power supply to the sewing machine is three-phase, the U-phase is connected to the input part 21 of the first diode bridge 20, the V-phase is connected to the input part 22 of the first diode bridge 20, and the W-phase is connected to the three-phase The two diodes 511 and 512 of the phase-use rectifier circuit 51 are connected.

[Capacitor and manual switch]

Between the intermediate point of the capacitors 41 and 42 and the input unit 22 of the first diode bridge 20, as described above, there is provided a manual switch 43 that switches between the short-circuit state and the open-circuit state.

The manual switch 43 switches to a short-circuit state when the AC power supply 12 is in the (1) single-phase 100V voltage range to perform voltage doubler rectification, and when the AC power supply 12 is in (2) the single-phase 200V voltage range (200-240V) or (3) In the case of the three-phase 200V voltage range, it switches to the open-circuit state and performs full-wave rectification.

When the manual switch 43 is in a short-circuit state, when the output of the AC power supply 12 is at a positive potential, the current flows from the input unit 21 of the first diode bridge 20 through the output unit 23, and further passes through the capacitor 41 and the manual switch. 43 and flow back to the path of the AC power source 12 .

In addition, when the output of the AC power supply 12 has a negative potential, current flows through the manual switch 43 and the capacitor 42 from the output section 24 of the first diode bridge 20 through the input section 21 and returns to the AC power supply 12 . .

As a result, voltage doubler rectification is performed, and the output side is boosted to DC 280V with respect to the AC 100V on the input side.

In addition, when the manual switch 43 is turned off, when the output of the AC power supply 12 is at a positive potential, the current flows from the input portion 21 of the first diode bridge 20 through the output portion 23, and further passes through the capacitor 41, 42 , which flows from the output portion 24 of the first diode bridge 20 through the input portion 22 and returns to the path of the AC power source 12 .

In addition, when the output of the AC power supply 12 has a negative potential, the current passes through the output unit 23 from the input unit 22 of the first diode bridge 20 , and then passes through the capacitors 41 and 42 , and then passes through the output unit of the first diode bridge 20 . The portion 24 flows through the input portion 21 and returns to the path of the AC power source 12 .

As a result, full-wave rectification is performed, and the output side is boosted to DC 280V with respect to the AC 200V on the input side.

[Second diode bridge]

The second diode bridge 30 includes a diode 35 that connects the anode terminal to the input unit 31 and the cathode terminal to the output unit 33 , and a diode 36 that connects the anode terminal to the output unit 34 and the cathode terminal to the input unit 31 Connections; a diode 37 which connects the anode terminal to the input part 32 and the cathode terminal to the output part 33 ; and a diode 38 which connects the anode terminal to the output part 34 and the cathode terminal to the input part 32 .

The input unit 31 of the second diode bridge 30 is connected to the AC power supply 12 together with the input unit 21 of the first diode bridge 20 , and the input unit 32 of the second diode bridge 30 is connected to the input unit 22 of the first diode bridge 20 together Connect to the AC power source 12 . Thus, the first diode bridge 20 and the second diode bridge 30 are connected to the AC power supply 12 in a parallel state.

Two resistors 45 and 46 connected in series are provided between the output unit 33 and the output unit 34 of the second diode bridge 30 , and the voltage detection unit 44 detects the potential difference across the resistor 46 .

With the configuration of the second diode bridge 30 and the resistors 45 and 46 described above, the voltage detection unit 44 can reduce the power supply voltage rectified by the first diode bridge 20 and the capacitors 41 and 42 to a value reduced by a fixed ratio. test.

[judgment department]

The voltage detection unit 44 is connected to the determination unit 53 , and the detection voltage is input to the determination unit 53 .

The determination unit 53 monitors the time-series change of the detected voltage from the voltage detection unit 44, and based on the change of the detected voltage, determines whether the AC power supply 12 is in (1) a single-phase 100V voltage region, (2) a single-phase 200V voltage region, (3) Which of the three-phase 200V voltage domains is determined.

Here, the method of determination by the determination part 53 is demonstrated. The determination part 53 records the detection voltage of the voltage detection part 44 in time series. Here, FIG. 2 shows a record of the change of the detection voltage when the AC power source 12 is in the (1) single-phase 100V voltage domain, and FIG. 3 shows the change in the detection voltage when the AC power source 12 is in the (2) single-phase 200V voltage domain. The record of the change of the detected voltage, FIG. 4 shows the record of the change of the detected voltage when the AC power supply 12 is in the (3) three-phase 200V voltage range.

Taking FIG. 2 as an example, first, the determination unit 53 obtains the minimum potential V1, which is the minimum value of the detected voltage, and calculates the minimum potential time T1, which is the period during which the minimum potential V1 continues. The minimum potential time T1 can be obtained by obtaining the period from the minimum potential V1 to the potential of the predetermined increase width α, that is, the period during which the potential is in the range of V1 to V1+α.

Similarly, the determination unit 53 obtains the maximum potential Vh, which is the maximum value of the detected voltage, and calculates the maximum potential time Th, which is a period during which the maximum potential Vh continues. The maximum potential time Th can be obtained by obtaining the period from the maximum potential Vh to the potential of the predetermined decrease width β, that is, the period during which the potential is in the range of Vh-β to Vh.

For example, in the case of (1) single-phase 100V voltage domain, (2) single-phase 200V voltage domain, and (3) three-phase 200V voltage domain, the following numerical values can be obtained as an example.

(1) In the case of single-phase 100V voltage domain, maximum potential: 2.5V, maximum potential time 4ms, minimum potential: 1.25V, minimum potential time 10ms, repetition time 20ms (described later)

(2) In the case of single-phase 200V voltage domain, maximum potential: 2.5V, maximum potential time 4ms, minimum potential: 0.63V, minimum potential time 1.5ms, repetition time 10ms (described later)

(3) In the case of three-phase 200V voltage domain, maximum potential: 2.5V, maximum potential time 12ms, minimum potential: 0.63V, minimum potential time 2ms, repetition time 20ms (described later)

As can be seen from the above example, the minimum potential time is significantly different depending on whether it is voltage doubler rectification or full-wave rectification. Therefore, the determination unit 53 determines a threshold value for the minimum potential time in advance (for example, about 4 to 8 ms, which is set to 6 ms here). It can be determined that the voltage-doubling rectification is performed when the threshold value is greater than or equal to the threshold value, and the full-wave rectification is performed when the threshold value is smaller than the threshold value.

In addition, it can be determined whether the AC voltage of the AC power supply 12 is in the 100V voltage range (the above (1)) or the 200V voltage range (the above (2) or (3)) depending on which of the voltage doubler rectification and the full-wave rectification is performed. .

Since the maximum potential time is significantly different depending on whether it is single-phase or three-phase, the determination unit 53 determines a threshold value (for example, about 6 to 10 ms, here, 8 ms) for the maximum potential time in advance, and can determine that the maximum potential time is greater than or equal to 8 ms. In the case of this threshold value, the number of phases of the AC power supply 12 is three-phase (the above (3)), and when it is less than the threshold value, the number of phases is one phase (the above-mentioned (1) or (2)).

As described above, by distinguishing between the minimum potential time and the maximum potential time, the determination unit 53 can determine (1) the single-phase 100V voltage domain, (2) the single-phase 200V voltage domain, and (3) the three-phase 200V voltage domain. All are identified.

Then, the determination unit 53 can obtain the power supply frequency of the AC power supply 12 based on the determination results of the voltage domains of the above (1) to (3) and the detection voltage of the voltage detection unit 44 .

That is, the determination unit 53 obtains the power supply frequency of the AC power supply 12 by obtaining the repetition period of the continuous waveform.

Specifically, as shown in FIGS. 2 to 4 , from the detection of the change in the detection voltage, the repetition time Tf from the detection of the minimum potential Vl (or the maximum potential) to the detection of the next minimum potential Vl is calculated.

Furthermore, when the voltage domain is (1) the single-phase 100V voltage domain, the determination unit 53 performs (power supply cycle)=(repetition time Tf) on the power supply frequency (=1/Tf) based on the reciprocal of the repetition time Tf. calculate.

In addition, when the voltage domain is (2) the single-phase 200V voltage domain, the determination unit 53 calculates the power supply frequency (=1 based on the reciprocal of the repetition time 2·Tf) because (power supply cycle)=(repetition time Tf)×2 /(2·Tf)) to calculate.

In addition, when the voltage domain is (3) the three-phase 200V voltage domain, since (power supply cycle)=(repetition time Tf), the determination unit 53 calculates the power supply frequency (=1/Tf) based on the reciprocal of the repetition time Tf calculate.

For example, when the repetition time Tf=20 [ms] is obtained and the voltage domain is (1) the single-phase 100 V voltage domain, the power supply frequency 50 [Hz] can be calculated from 1/Tf=1/20 [ms].

Similarly, when the repetition time Tf=10 [ms] and the voltage domain is (2) the single-phase 200V voltage domain, it can be calculated from 1/(2·Tf)=1/(2·10)[ms] When the power frequency is 50 [Hz], the repetition time Tf = 20 [ms], and the voltage domain is (3) the three-phase 200 V voltage domain, the power frequency 50 [ Hz].

[Motor drive circuit]

The aforementioned three-phase rectifier circuit 51 is connected to a motor drive circuit 52 serving as a motor control unit. The motor drive circuit 52 has a function in principle. A speed command is input from a control device of the sewing machine (not shown), and the current of the sewing machine motor 11 is controlled so that the acceleration corresponding to the difference between the current sewing machine motor 11 and the command speed is obtained. to accelerate. Thereby, the sewing machine motor 11 can be driven so that it may become the target speed indicated by the speed command of the control device.

Then, the identification results of (1) single-phase 100V voltage domain, (2) single-phase 200V voltage domain, and (3) three-phase 200V voltage domain are input from the determination unit 53 to the motor drive circuit 52 .

That is, the motor drive circuit 52 sets different coefficients K1, K2, and K3 for (1) the single-phase 100V voltage domain, (2) the single-phase 200V voltage domain, and (3) the three-phase 200V voltage domain, respectively, and the sewing machine motor 11 The control is performed according to the acceleration obtained by multiplying the coefficients K1, K2, K3 corresponding to the recognition results and the "acceleration corresponding to the difference between the current sewing machine motor 11 and the command speed" in the current control of the sewing machine motor 11 described above. accelerate.

The magnitudes of the coefficients K1, K2, and K3 are set to K1<K2<K3. That is, when the AC power supply 12 is in the (1) single-phase 100V voltage range, the speed control for accelerating at low acceleration is performed, and when the AC power supply 12 is in the (2) single-phase 200V voltage range, medium acceleration is performed. The speed control for acceleration is performed, and when the AC power source 12 is in the (3) three-phase 200V voltage range, the speed control for acceleration at high acceleration is performed.

This is because, when accelerating the sewing machine motor 11 , the greater the acceleration, the greater the amount of current flowing from the AC power source 12 , and the greater the load on the AC power source 12 .

That is, regarding the AC power supply 12 , the higher the AC voltage, the larger the current that can flow, and the larger the number of phases, the larger the current that can flow.

Therefore, the motor drive circuit 52 suppresses the acceleration in the (1) single-phase 100V voltage region where the current that can flow is the smallest, and increases the acceleration in the (3) three-phase 200V voltage region where the current that can flow is the largest. Regardless of the voltage range of the AC power source 12, the sewing machine motor 11 can be controlled so as to reduce the generation of the load.

[The role of the power circuit of the sewing machine motor]

When the power supply circuit 10 of the sewing machine motor is used, first, the manual switch 43 is switched according to the voltage range of the AC voltage of the AC power supply 12 . That is, the operator of the sewing machine determines which of the voltage-doubling rectification and the full-wave rectification is to be performed, and performs the switching operation of the manual switch 43 .

As a result, the voltage doubler rectification is performed when the AC power source 12 is in the (1) single-phase 100V voltage domain, and is executed when the AC power source 12 is in the (2) single-phase 200V voltage domain or (3) three-phase 200V voltage domain. Full wave rectification.

The voltage detection unit 44 performs voltage detection, and performs voltage detection with the waveform shown in FIG. 2 when the AC power supply 12 is in the (1) single-phase 100V voltage range, and when the AC power supply 12 is in the (2) single-phase 200V voltage range Next, voltage detection is performed with the waveform shown in FIG. 3 , and when the AC power supply 12 is in the (3) three-phase 200V voltage range, the voltage detection is performed with the waveform shown in FIG.

The determination unit 53 calculates the minimum potential V1, the minimum potential time T1, the maximum potential Vh, and the maximum potential time Th based on the voltage detection from the voltage detection unit 44, and compares them with the thresholds, respectively, and determines that the AC power supply 12 is (1) single-phase. Which of the 100V voltage domain, (2) the single-phase 200V voltage domain, and (3) the three-phase 200V voltage domain is determined and input to the motor drive circuit 52 .

The motor drive circuit 52 selects the coefficients K1 to K3 in accordance with the determination result of the determination unit 53, and executes the speed control of the sewing machine motor 11 in accordance with the acceleration multiplied by the coefficients.

[Technical effect of invention]

As described above, the power supply circuit 10 of the sewing machine motor includes: the first diode bridge 20 connected to the AC power supply 12; the two capacitors 41 and 42 connected to the output parts 23 and 24 of the first diode bridge 20; The manual switch 43 of the switching section switches the middle of the two capacitors 41 and 42 and the input section 22 of the first diode bridge 20 between the short-circuit state and the open-circuit state; the second diode bridge 30; the voltage detection section 44, which Detects the voltages of the two output parts 33 and 34 of the second diode bridge 30; ), according to the minimum potential time T1 to determine whether the manual switch 43 is in a voltage-doubling rectification state or a full-wave rectification state; Output control of the motor.

Therefore, the motor drive circuit 52 capable of recognizing the voltage range of the AC voltage of the AC power supply 12 can control the sewing machine motor 11 so as to further reduce the load on the AC power supply 12 according to the voltage range of the AC voltage.

In addition, even when a facility such as a sewing factory using a plurality of sewing machines is connected to an AC power source to supply power to the sewing machine motor 11, the occurrence of voltage drop (voltage fluctuation) in the power supply can be reduced, and the plurality of sewing machines can be Make good sewing.

Then, the determination unit 53 obtains the duration of the maximum potential Vh (maximum potential time Th) when the detection voltage of the voltage detection unit 44 changes continuously, and determines the number of phases of the AC power supply 12 based on the maximum potential time Th, and the motor drive circuit 52 The output control of the sewing machine motor 11 is performed according to the number of phases of the AC power supply 12 obtained by the determination unit 53 , so that the sewing machine motor 11 can be controlled so as to reduce the load on the AC power supply 12 according to the number of phases.

Therefore, even in an environment in which a plurality of sewing machines are used, the occurrence of voltage drop (voltage fluctuation) in the power supply can be reduced, and better sewing can be performed.

In addition, since the determination unit 53 can recognize which voltage range of the AC voltage of the AC power supply 12 is in the voltage range, it is possible to obtain the repetition period of the continuous waveform from the detected voltage of the voltage detection unit 44 , so that the voltage range of the AC power supply 12 can also be obtained. power frequency.

[other]

In addition, the determination unit 53 obtains the type of the voltage domain of the AC voltage of the AC power source 12 , but it is also possible to obtain the AC voltage of the AC power source in more detail in the voltage domain instead of the voltage domain of the AC voltage.

That is, the determination unit 53 obtains the time-series change of the detection voltage from the voltage detection unit 44 and obtains the maximum potential Vh. However, since the value of the maximum potential Vh has a correlation with the value of the AC voltage of the AC power supply, the determination unit 53 obtains the maximum potential Vh. The value of the AC voltage of the AC power source can be obtained from the value of the maximum potential Vh by providing a storage unit that stores a table in which the correspondence between the value of the maximum potential Vh and the value of the AC power supply voltage is recorded. From the value of the maximum potential Vh, the value of the AC voltage of the AC power supply can be obtained with an accuracy of about 1 [V] unit. Therefore, for example, in the (1) single-phase 100V voltage range, the value of the AC voltage is in the range of 100 to 120V. range, the value can be determined in 1[V] units. The same applies to the voltage domains of the other (2) and (3).

Claims (2)

1. A power supply circuit for a sewing machine motor, comprising:

a 1 st diode bridge having two input parts connected to an alternating current power supply and two output parts connected to a load;

two capacitors connected in series between two outputs of the 1 st diode bridge;

a switching unit that switches the middle of the two capacitors and one input unit of the 1 st diode bridge between a short-circuit state and an open-circuit state;

a 2 nd diode bridge having two input parts connected to the ac power supply in parallel with the 1 st diode bridge; and

a voltage detection unit for detecting voltages of the two output units of the 2 nd diode bridge,

the power circuit of the sewing machine motor comprises:

a determination unit that obtains a duration of a minimum potential when the voltage detected by the voltage detection unit continuously changes, and determines whether the switching unit is in a voltage doubler rectification state or a full-wave rectification state based on the duration of the minimum potential; and

and a motor control unit for controlling the output of the motor of the sewing machine based on the rectified state obtained by the determination unit.

2. The power supply circuit for a sewing machine motor according to claim 1,

the determination unit determines a duration of a maximum potential when the voltage detected by the voltage detection unit continuously changes, determines the number of phases of the AC power supply based on the duration of the maximum potential,

the motor control unit controls the output of the motor of the sewing machine based on the number of phases of the ac power supply determined by the determination unit.

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